The Historical Sense:

Yet if the only form of tradition, of handing down, consisted in following the ways of the immediate generation before us in a blind or timid adherence to its successes, "tradition" should positively be discouraged. . . . Tradition is a matter of much wider significance. It cannot be inherited, and if you want it you must obtain it by great labour. It involves, in the first place, the historical sense, which we may call nearly indispensable to any one who would continue to be a poet beyond his twenty-fifth year; and the historical sense involves a perception, not only of the pastness of the past, but of its presence; the historical sense compels a man to write not merely with his own generation in his bones, but with a feeling that the whole of the literature of Europe from Homer and within it the whole of the literature of his own country has a simultaneous existence and composes a simultaneous order. This historical sense, which is a  sense of the timeless as well as of the temporal and of the timeless and of the temporal together, is what makes a writer traditional. And it is at the same time what makes a writer most acutely conscious of his place in time, of his own contemporaneity.
. . . the past should be altered by the present as much as the present is directed by the past.
The poet. . . . must be quite aware of the obvious fact that art never improves, but that the material of art is never quite the same. . . . What happens is a continual surrender of himself as he is at the moment to something which is more valuable. The progress of an artist is a continue self-sacrifice, a continual extinction of personality.
Emotion and Personality in Poetry:
There is a great deal, in the writing of poetry which must be conscious and deliberate. In fact, the bad poet is usually unconscious where he ought to be conscious, and conscious where he ought to be unconscious. Both errors tend to make him "personal." Poetry is not a turning loose of emotion, but an escape from emotion; it is not the expression of personality, but an escape from personality. But, of course, only those who have personality and emotions know what it means to want to escape from these things.
. . . the poet. . . . is not likely to know what is to be done unless he lies in what is not merely the present, but the present moment of the past, unless he is conscious, not of what is dead, but of what is already living.
The artistic "inevitability" lies in this complete adequacy of the external to the emotion; and this is precisely what is deficient in Hamlet. Hamlet (the man) is dominated by an emotion which is inexpressible, because it is in excess of the facts as they appear. . . . The intense feeling, ecstatic or terrible, without an object or exceeding its object, is something which every person of sensibility has known; it is doubtless a subject of study for pathologists. It often occurs in adolescence: the ordinary person puts these feelings to sleep, or trims down his feelings to fit the business world; the artist keeps them alive by his ability to intensify the world to his emotions.
The second-rate artist, of course, cannot afford to surrender himself to any common action; for his chief task is the assertion of all the trifling differences which are his distinction: only the man who has so much to give that he can forget himself in his work can afford to collaborate, to exchange, to contribute.
The possessors of the inner voice ride ten in a compartment to a football match at Swansea, listening to the inner voice, which breathes the eternal message of vanity, fear, and lust.
Education vs. Convention:
It is important that the artist should be highly educated in his own art; but his education is one that is hindered rather than helped by the ordinary processes of society which constitute education for the ordinary man. For these processes consist largely in the acquisition of impersonal ideas which obscure what we really are and feel, what we really want, and what really excites our interest. It is of course not the actual information acquired, but the conformity which the accumulation of knowledge is apt to impose that is harmful.
Purpose of Imaginative Work:
The author of a work of imagination is trying to affect us wholly, as human beings, whether he knows it or not; and we are affected by it, as human beings, whether we intend to be or not. . . . Wide reading is not valuable as a kind of hoarding, an accumulation of knowledge, or what sometimes is meant by the term "a well-stocked mind." It is valuable because in the process of being affected by one powerful personality after another, we cease to be dominated by any one, or by any small number. The very different views of life, cohabiting in our minds, affect each other, and our own personality asserts itself and gives each a place in some arrangement peculiar to ourself.
Though we may read literature merely for pleasure, of "entertainment" or of "aesthetic enjoyment," this reading never affects simply a sort of special sense: it affects us as entire human beings; it affects our moral and religious existence.
On Dante:
The experience of a poem is the experience both of a moment and of a life-time. It is every much like our intenser experiences of other human beings. There is a first, or an early moment which is unique, of shock and surprise, even of terror (Ego dominus tuus): and yet which would become destitute of significance if it did not survive in a larger whole of experience; which survives inside a deeper and calmer feeling. The majority of poems one outgrows and outlives, as one outgrows and outlives the majority of human passions: Dante's is one of those which one can only just hope to grow up to at the end of life.
For the science of art of writing verse, one has learned from the Inferno that the greatest poetry can be written with the greatest economy of words, and with the greatest austerity in the use of metaphor, simile, verbal beauty and elegance.
The language of each great English poet is his own language; the language of Dante is the perfection of a common language . . . . From the Purgatorio one learns that a straightforward philosophical statement can be great poetry. . . . And gradually we come to admit that Shakespeare understands a greater extent and variety of human life than Dante; but that Dante understands deeper degrees of degradation and higher degrees of exaltation.
These are from Eliot's essays "Tradition and the Individual Talent" (1919), "The Function of Criticism" (1923), "Hamlet and His Problems" (1919), "William Blake" (1920), "Dante" (19239), and "Religion and Literature" (1935). Notice that three of these essays were published within three years of "Prufrock."